The present invention is related to a wavelength to optical power converter and a method thereof, and more particularly to a fiber-optic winding wavelength to optical power converter and a method for converting the wavelength into the optical power in a fiber-optic communication system.
The present Dense Wavelength Division Multiplexing (DWDM) system is adopted by using a 100/200 GHz channel spacing and is capable of operating in a long-term and acquiring a crosstalk specification. A distributed feedback (DFB) is capable of being normally operated in a short-term but a wavelength drift will be generated over a long period of time. Therefore, it is important and necessary to monitor an actual operating wavelength of the DWDM system. Consequently, it would be an urgent issue how to stably operate in a fiber-optic broadband network which is of a gradually raised demand in the market, besides adding the fiber-optic bandwidth.
Presently, an interferometer and a Fiber Bragg Grating (FBG) sensor such as a Fabry-Perot interferometer and a linear FBG are adopted for being regarded as a wavelength discriminator to convert a variable signal of the distributed feedback (DFB) laser wavelength variation into a variable optical intensity. Therefore, the practical operation of the wavelength discriminator in a Wavelength Division Multiplexing (WDM) fiber-optic network is a future tendency and the present invention is a practical application in relation to this field.
Many wavelength detecting techniques are applied in the Wavelength Division Multiplexing/Dense Wavelength Division Multiplexing (WDM/DWDM) broadband fiber-optic network, but active components or passive components developed by these wavelength detecting techniques are more complicated to be not easily obtainable or identifiable by the users. Consequently, these techniques don""t include better practicability and technical maturity. Certain other techniques include a higher price level and the cost thereof is difficult to be reduced.
A real time and full wave-band wavelength monitoring system including a 0.076 nm/dB resolution, 0.02 nm precision, 16 channels and 200 GHz channel spacing and composed of a Phased Array Wavelength Grating (PAWG), an array of 32 detectors and an A/D (alternating current/direct current) converter of 64 channels is disclosed by Shan Zhong, Chau-Han Lee, Xiao-Hui Yang, Yung-Jui Chen and Dennis Stone, in xe2x80x9cIntegrated real time multi-channel wavelength monitoring circuit using phased-array waveguide gratingxe2x80x9d, Digest of Optical Fiber Communication, Volume 3, 1997, pages 30-32. The PAWG accomplished by a double WDM channel resolution and an xcex1/2 angle difference is capable of covering full wave-band frequency spectrum to generate two differential curves by using a drift of a central wavelength at the halfway of the channel spacing to confirm the convergence of the blind spot. The system is used for a real time and full wave-band wavelength monitoring in the DWDM system. This wavelength detecting method by using an Array Wavelength Grating (AWG) is a more complicated, undeveloped technique and easily affected by the environment temperature so that it has a lower reliability and includes a more expensive cost.
A simple method of stabilizing wavelength used for monitoring and controlling the wavelength of the DWDM system in order to solve an output or a display of a long-wavelength drift over the limit of a free-running DFB laser transmitter is disclosed by B. Villeneuve, H. B. Kim, M. Cry and D. Gariepy, in xe2x80x9cA Compact Wavelength Stabilization Scheme for Telecommunication Transmittersxe2x80x9d, Digest of the IEEE/LEOS Summer Topical Meeting, 1997, pages 19-20. The method includes the steps of providing two very close optical diodes, capturing two spectral responses by using a periodic transmissive frequency response of a Fabry-Perot (FP) filter, and calculating a measurable wavelength value via the difference between the two spectral responses. A unit is independently existent under the above-mentioned conception and can be merged into an existent laser module without an extra electric power because of its tiny volume. But the unit includes a high level of manufacturing technique, a highly difficult components assembly, a high rejection rate and a higher cost and is difficult for sourcing components to maintain. Consequently, because the unit does not arrive at the stage of being put in mass production and practical application yet, it is not proper to be applied in a local area network (LAN), i.e. Fiber to the Home (FTTH) WDM/DWDM network system, and particularly to be the consumer end without any professional backgrounds.
A wavelength monitoring technique by using a relation between a carrier from a semiconductor optical amplifier and an incident optical wavelength, and detecting a transmission point of the semiconductor optical amplifier to measure and track the wavelength in the DWDM system is disclosed by San-Liang Lee, Ching-Tang Pien and Yu-Yi Hsu, in xe2x80x9cWavelength monitoring with low cost laser diodes for DWDM applicationsxe2x80x9d, Electronics Letters, Volume 36, Issue 6, 2000. Consequently, the above-mentioned purpose is achieved by biasing a laser diode under the threshold limit value (TLV) or using the semiconductor optical amplifier on an anti-reflective coating layer. Moreover, it also is very suitable to detect the discontinuous or separate components by using the external wavelength or stabilizing the wavelength of the laser diode.
This kind of wavelength monitoring technique is capable of being used to discriminate the operating interface thereof by using the fixed bias or scan the mode type. This technique is used for stabilizing the wavelength with regard to the wavelength drift because of a lower cost of the laser diode, but the semiconductor optical amplifier used therein is very expensive. Therefore, it is not suitable to be applied to the wavelength detection in the general local area network (LAN).
A wavelength meter having multiple wavelength laser inputs is disclosed by Hackel et al., in xe2x80x9cWavelength meter having single mode fiber optics multiplexed inputsxe2x80x9d, U.S. Pat. No. 5,189,485, filed on Feb. 21, 1991. This wavelength meter has a multiplexer to remote-control multiple lasers via a single mode fiber-optic for inputting one of the plurality of laser beam signal inputs into a wavelength measuring device, and thus is capable of improving the calibration capability of the wavelength measuring device in a real-time and online manner by referring to a predetermined laser beam wavelength. Thus, the wavelength measuring technique includes a practicability and is available by the present invention having a lower cost.
A method and apparatus for determining the wavelength of optical radiation, i.e. the visible radiation light are disclosed by Varnham, in xe2x80x9cDetermining the wavelength of optical radiationxe2x80x9d, U.S. Pat. No. 5,022,754, filed on Aug. 7, 1989. The optical radiation is subjected to two or more wavelength dependent phase modulations having a net effect which is wavelength dependent and is zero at a predetermined wavelength. The net modulation is then determined so as to obtain the difference between the predetermined wavelength and the actual wavelength of the optical radiation. However, it is difficult for one skilled in the modulation technique so that it does not include a practicability.
A microprocessor having an interferometer with linearizing interference fringe pattern for determining the wavelength of laser light is disclosed by Kachanov, in xe2x80x9cInterferometer with processor for linearizing fringers for determining the wavelength of laser lightxe2x80x9d, U.S. Pat. No. 5,420,687, filed on Oct. 4, 1993. The interference fringe pattern is detected by a charge-coupled device (CCD) array and is sent to a computer to be processed. The computer compares the result to determine the wavelength of laser light.
The above-mentioned papers and patents are the presently main techniques for monitoring and measuring the wavelength in Wavelength Division Multiplexing (WDM). However, some of those techniques are too expensive to having practicability. Moreover, some key components used in the techniques include complex manufacturing process and cannot be obtained easily. Further, variant factors affecting the above-mentioned system are very complex and don""t include a high stability so that they are not easily controllable.
It is therefore tried by the applicant to deal with the above situations encountered in the prior art.
It is therefore an object of the present invention to provide a simple, lower cost and practical wavelength to optical power converter and a method for converting the wavelength into the optical power by applying a bending property of single mode and spiral fiber to output different optical powers in response to different input wavelength signals.
It is another object of the present invention to provide the wavelength to optical power converter and the method for converting the wavelength into the optical power operated in broadband channel form 750 nm to 1750 nm to have a good one to one mapping relation between the wavelength and the optical power.
It is another object of the present invention to provide the wavelength to optical power converter and the method for converting the wavelength into the optical power by applying a working principle based on the single mode intrinsic bending loss.
According to an aspect of the present invention, there is provided a wavelength to optical power converter used for monitoring the wavelength and the optical power in a fiber-optic communication system. The wavelength to optical power converter includes an input fiber pigtail for inputting an optical wavelength signal, a spiral fiber connected to the input fiber pigtail, a cylinder for fixing the spiral fiber, an output fiber pigtail extended from the spiral fiber, and an optical detector connected to the output fiber pigtail for reading a signal from the output fiber pigtail to generate the optical power, wherein the spiral fiber outputs the optical power in response to the optical wavelength signal, thereby performing a conversion from the wavelength into the optical power.
Preferably, the spiral fiber is wrapped around a fixed radius of the cylinder.
Preferably, the fixed radius of the cylinder is smaller than 10 mm when the optical wavelength signal is in the range between 750 nm and 1300 nm, and the fixed radius of the cylinder is more than 10 mm when the optical wavelength signal is in the range between 1300 nm and 1750 nm.
Preferably, the optical wavelength signal includes a wave-band range between 750 nm and 1750 nm.
Preferably, the optical wavelength signal is a monochromatic light source having a wave-band range between 750 nm and 1750 nm.
Preferably, the optical detector is an optical power reading device.
Preferably, the wavelength to optical power converter further includes a fluorescent sensing head and an optical sensor to form a medical sensor of a medical sensing system.
Preferably, the wavelength to optical power converter further includes a tunable light source, an optical sensor and a feedback control system of the optical power to form a stabilizing frequency network of a stabilized frequency system of a Wavelength Division Multiplexing (WDM) network.
Preferably, the wavelength to optical power converter further includes a tunable light source, an optical sensor and a processor with a corresponding relationship between the optical power to the wavelength to form a wavelength detecting system of a Wavelength Division Multiplexing (WDM) network for measuring the wavelength and monitoring the WDM network.
Preferably, the wavelength to optical power converter further includes a Wavelength Division Multiplexing (WDM) multiplexer, an optical access multiplexer, a Wavelength Division Multiplexing (WDM) demultiplexer, a first attenuator and a second attenuator and two Erbium-doped fiber amplifiers (EDFAs) to form a network attenuator of a Wavelength Division Multiplexing (WDM) network.
According to another aspect of the present invention, there is provided a method for converting a wavelength into an optical power used in a wavelength to optical power converter of a fiber-optic communication system, wherein the wavelength to optical power converter includes an input fiber pigtail, a spiral fiber, a cylinder, an output fiber pigtail and an optical detector. The method includes steps of inputting a specific wave-band monochromatic light source to the input fiber pigtail, measuring a bending loss of the spiral fiber, regulating a specific parameter and calculating a theory curve, and reading a signal via the optical detector to generate an optical power output signal.
Preferably, the specific wave-band monochromatic light source is in the range between 750 nm and 1750 nm.
Preferably, the specific parameter includes a bending radius, a winding number and a fiber-optic specification.
Preferably, the fiber-optic specification includes an admitted level of a fiber-optic to the bending loss thereof which is a variation of the bending loss against different spatial interferences.
Preferably, the theory curve is a mathematical equation which is a simulated semi-empirical theory curve obtained by getting actual input/output (I/O) values of the fiber-optic communication system and regulating the specific parameter for showing a conversion relationship between the wavelength and the optical power in different input/output (I/O) values.
Preferably, the mathematical equation is a general formula of L(W)=xcex61W3+xcex62W2+xcex63W+xcex64, wherein L(W) is a bending loss value, W is an input wavelength and xcex6i(i=1,2,3,4) is a specific parameter when the input wavelength is in the range between 750 nm and 1300 nm, and is a general formula of L(W)=xcex61N exp(xcex8N+xcex62Wxe2x88x92xcex63R), wherein L(W) is a bending loss value, W is an input wavelength, xcex6i(i=1,2,3) is a specific parameter, R is a bending radius, N is a winding number and xcex8N is a winding angle when the input wavelength is in the range between 1300 nm and 1750 nm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the input wavelength which is L(W)=xe2x88x922.118xc3x9710xe2x88x928W3+7.6504xc3x9710xe2x88x924W2xe2x88x920.0936W+39.2805, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 3 and the bending radius is 12.5 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x924.3102xc3x9710xe2x88x928W3+1.4356xc3x9710xe2x88x924W2xe2x88x920.1653W+64.0322, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 5 and the bending radius is 12.5 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x921.9511xc3x9710xe2x88x9210W3xe2x88x928.3908xc3x9710xe2x88x927W2xe2x88x920.0014W+0.9694, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 10 and the bending radius is 12.5 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x922.3069xc3x9710xe2x88x928W3+8.2415xc3x9710xe2x88x925W2xe2x88x920.0996W+41.1952, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 3 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x922.2554xc3x97108W3+8.1316xc3x9710xe2x88x925W2xe2x88x920.0993W+41.5358, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 5 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x922.7325xc3x9710xe2x88x928W3+9.6101xc3x9710xe2x88x925W2xe2x88x920.1142W+46.6043, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 7 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the betiding loss and the wavelength which is L(W)=xe2x88x922.29xc3x9710xe2x88x928W3+8.1705xc3x9710xe2x88x925W2xe2x88x920.0989W+41.1294, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 10 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x921.6393xc3x9710xe2x88x928W3+6.2443xc3x9710xe2x88x925W2xe2x88x920.0803W+35.2693, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 13 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x921.7899xc3x9710xe2x88x928W3+6.6879xc3x9710xe2x88x925W2xe2x88x920.0843Wxe2x88x9236.3340, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 15 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the bending loss and the wavelength which is L(W)=xe2x88x922.2137xc3x9710xe2x88x928W3+7.9569xc3x9710xe2x88x925W2xe2x88x920.0969W+40.4603, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 18 and the bending radius is 6.8 mm.
Preferably, the conversion relationship between the wavelength and the optical power is a mathematical equation of a relative curve of the loss and the light source wavelength which is L(W)=xe2x88x923.3952xc3x9710xe2x88x928W3+1.1996xc3x9710xe2x88x924W2xe2x88x920.1438W+59.2077, wherein L(W) is a bending loss value, W is an input wavelength when the input wavelength is in the range between 750 nm and 1300 nm, the winding number is 20 and the bending radius is 6.8 mm.
According to a further aspect of the present invention, there is provided a wavelength to optical power converter used for measuring a wavelength. The wavelength to optical power converter includes an input fiber pigtail for inputting an optical wavelength signal, a spiral fiber connected to the input fiber pigtail, a cylinder for fixing the spiral fiber, an output fiber pigtail extended from the spiral fiber, and an optical detector connected to the output fiber pigtail for reading a signal from the output fiber pigtail to generate an optical power, wherein the spiral fiber outputs the optical power in response to the optical wavelength signal, thereby performing the conversion from the wavelength into the optical power.
The present invention may best be understood through the following descriptions with reference to the accompanying drawings, in which: